Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/2595#discussion_r18297121
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/tree/DecisionTree.scala ---
@@ -518,30 +512,69 @@ object DecisionTree extends Serializable with Logging
{
agg
}
- // Calculate bin aggregates.
- timer.start("aggregation")
- val binAggregates: DTStatsAggregator = {
- val initAgg = if (metadata.subsamplingFeatures) {
- new DTStatsAggregatorSubsampledFeatures(metadata,
treeToNodeToIndexInfo)
- } else {
- new DTStatsAggregatorFixedFeatures(metadata, numNodes)
+ /**
+ * Get node index in group --> features indices map,
+ * which is a short cut to find feature indices for a node given node
index in group
+ * @param treeToNodeToIndexInfo
+ * @return
+ */
+ def getNodeToFeatures(treeToNodeToIndexInfo: Map[Int, Map[Int,
NodeIndexInfo]])
+ :Map[Int, Option[Array[Int]]] = {
+ val mutableNodeToFeatures = new mutable.HashMap[Int,
Option[Array[Int]]]()
+ treeToNodeToIndexInfo.values.foreach { nodeIdToNodeInfo =>
+ nodeIdToNodeInfo.values.foreach { nodeIndexInfo =>
+ mutableNodeToFeatures(nodeIndexInfo.nodeIndexInGroup) =
nodeIndexInfo.featureSubset
+ }
}
- input.treeAggregate(initAgg)(binSeqOp, DTStatsAggregator.binCombOp)
+ mutableNodeToFeatures.toMap
}
- timer.stop("aggregation")
// Calculate best splits for all nodes in the group
timer.start("chooseSplits")
+ // In each partition, iterate all instances and compute aggregate
stats for each node,
+ // yield an (nodeIndex, nodeAggregateStats) pair for each node.
+ // After a `reduceByKey` operation,
+ // stats of a node will be shuffled to a particular partition and be
combined together,
+ // then best splits for nodes are found there.
+ // Finally, only best Splits for nodes are collected to driver to
construct decision tree.
+ val nodeToFeatures = getNodeToFeatures(treeToNodeToIndexInfo)
+ val nodeToFeaturesBc = input.sparkContext.broadcast(nodeToFeatures)
+ val nodeToBestSplits =
+ input.mapPartitions { points =>
+ // Construct a nodeStatsAggregators array to hold node aggregate
stats,
+ // each node will have a nodeStatsAggregator
+ val numNodes = nodeToFeatures.keys.size
--- End diff --
numNodes has already been computed above; reuse that value in this closure?
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